Project Summary This proposal describes a five-year training plan for the development of an independent research career focused on the virus-host interactions that dictate susceptibility of the pediatric brain to infection. Specifically, the applicant strives to elucidate how viral genetic variation influences neurovirulence, both by altering viral function and inducing immune escape. The applicant is an attending Infectious Diseases physician at the Children's Hospital of Philadelphia (CHOP) with previous PhD training in basic neuroimmunology. The goals for this award are to develop and refine the essential skills that will be required for a successful career as an independent investigator, including expertise in sequencing and bioinformatic analysis of large genetic data sets, viral genome editing, and neurologically-relevant in vitro and in vivo models of viral infection. The mentors for this award include Dr. Matthew Weitzman, an internationally recognized leader in the field of virus-host interactions, and Dr. Dennis Kolson, a physician-scientist and expert in mechanisms of neurovirulence. To add depth and breadth to the scientific career guidance of the applicant, a scientific advisory committee is composed of scientists and physician-scientists from diverse and complementary fields. Dr. Akhtar will also benefit from the unparalleled resources and mentorship available at both CHOP and the University of Pennsylvania. The proposed research focuses on the role of viral genetic variability in determining the clinical manifestations of neonatal herpes simplex virus (HSV) disease, particularly the ability to infect the neonatal brain. HSV infection of the neonatal brain causes severe encephalitis and permanent neurologic deficits, but the factors that promote central nervous system (CNS) infection are not known. Recent studies show that substantial genetic variability exists within HSV genomes, but have not evaluated how these variations impact viral growth characteristics or human disease manifestations. Successful completion of the studies proposed will identify HSV genetic variations associated with neonatal CNS disease, determine their impact on viral spread between neurons, and their ability to alter progression to CNS infection. This will be accomplished by large-scale viral genomic sequencing to identify variations most frequently associated with CNS disease, followed by creation of mutant viruses to determine the individual impact of identified variations on viral spread between the simplified neuronal connections of in vitro chamber assays, and the complex neuronal circuits of the murine retina. The studies outlined in this proposal will provide the first insights into how variations in the neonatal HSV genome impact neurovirulence and the development of CNS disease.